The present invention relates to an image-forming apparatus such as a copy apparatus or a printer.
Generally, in such an image-forming apparatus that developer on a roller or a developer-holding member attached to the outer surface of the roller is brought into contact with a photosensitive drum to develop an electrostatic latent image on the drum to form a visible image, maintaining a distance between the drum and the roller constant along the axes thereof is necessary in order to form an image of uniform density.
In another image-forming apparatus in which an image-forming unit unitedly assembled by a photosensitive drum and a developing device is attached to a body of the apparatus, it is necessary for the unit to be accurately located with respect to the body and to connect the drum with a driving system of the body with good accuracy.
Therefore, conventionally, a distance between the drum and the roller is set to be constant by bringing contact members arranged at both the ends of the roller into contact with the drum. A positioning member of the unit is engaged with an engaging portion of the body, so that the unit is positioned to the body of the apparatus.
Deformation such as errors or torsion in manufacturing the body of the unit, however, causes the drum not to be positioned to the body of the apparatus with good accuracy, and thus looseness causes in engagement between a driving gear of the drum and a gear of the driving system of the body.